Area Lamp - Part 5
Posted 01.06.2019 by Mario & Kitty Costello
After the base was finished curing, the sections of the mold form were dis-assembled and removed. Everything looks fine. The metal spine that was placed in the back of the base took some convincing, but we had thought ahead and put threaded holes into the piece of aluminum that created that space, so all we had to do was slowly thread the screws into the holes and it pushed the part out of the molded form.
The base had a matte finish to it and now began the process of refining the form- we used a 5” angle grinder with sanding discs that have diamonds of various grits embedded into them and a dust shroud that hooks up to a vacuum cleaner to keep the dust down. The coarse grits allowed us to change further smooth the corners and increase the radius a bit while the finer grits brought the surface to a polish (video_1.mov). This was all done dry, but can be done with water to aid the process. The finer grits started to “smear” and turn the surface black during the process (probably from the binder on the sanding discs getting too hot), so we cleaned off the unwanted coloring and finished it by hand with some sponges that have a fine diamond coating on them. This process was done with water from a spray bottle to help lubricate things.
The large arc of the “spine” section came back from the metal fab shop that did the tube rolling for us and was right on target in terms of dimensions. The ends were slightly dis-figured from the rolling process, so a little had to be trimmed off. To strengthen the connection between the straight tube and the arc tube, we inserted a piece of 1018 steel tubing inside the brass tube- luckily the outer diameter of the round tube fit almost perfectly inside the square tube. And it allows the whole arc section to swing back and forth and adds some stiffness to the structure. Finally seeing the actual part leaning against the side of the shop, we were starting to worry about whether the whole thing was going to tip over or not. It was big. And heavy.
Here’s a detail of the connector that holds the glass globe- you can see that it allows everything to pivot in another axis. Here’s a detail of the whole assembly that holds the frosted glass globe in place along with the bulb and socket- we used one of our coaster bodies as the cap for this assembly!
The white balls are made from Delrin, another slippery plastic, and are meant to hold things “softly” with a bit of compliance so the globe doesn’t crack when secured.
And another detail shot showing how the brass tube fits into the recess that was part of the molding process .
The finished lamp now sits in our living room and works great! And we only bump our heads into it occasionally.